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263 lines
8.1 KiB
Go
263 lines
8.1 KiB
Go
package gosseract
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// #if __FreeBSD__ >= 10
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// #cgo LDFLAGS: -L/usr/local/lib -llept -ltesseract
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// #else
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// #cgo CXXFLAGS: -std=c++0x
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// #cgo LDFLAGS: -llept -ltesseract
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// #endif
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// #include <stdlib.h>
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// #include <stdbool.h>
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// #include "tessbridge.h"
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import "C"
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import (
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"fmt"
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"os"
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"strings"
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"unsafe"
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)
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// Version returns the version of Tesseract-OCR
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func Version() string {
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api := C.Create()
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defer C.Free(api)
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version := C.Version(api)
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return C.GoString(version)
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}
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// ClearPersistentCache clears any library-level memory caches. There are a variety of expensive-to-load constant data structures (mostly language dictionaries) that are cached globally – surviving the Init() and End() of individual TessBaseAPI's. This function allows the clearing of these caches.
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func ClearPersistentCache() {
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api := C.Create()
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defer C.Free(api)
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C.ClearPersistentCache(api)
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}
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// Client is argument builder for tesseract::TessBaseAPI.
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type Client struct {
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api C.TessBaseAPI
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// Holds a reference to the pix image to be able to destroy on client close
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// or when a new image is set
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pixImage C.PixImage
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// Trim specifies characters to trim, which would be trimed from result string.
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// As results of OCR, text often contains unnecessary characters, such as newlines, on the head/foot of string.
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// If `Trim` is set, this client will remove specified characters from the result.
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Trim bool
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// TessdataPrefix can indicate directory path to `tessdata`.
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// It is set `/usr/local/share/tessdata/` or something like that, as default.
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// TODO: Implement and test
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TessdataPrefix *string
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// Languages are languages to be detected. If not specified, it's gonna be "eng".
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Languages []string
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// Variables is just a pool to evaluate "tesseract::TessBaseAPI->SetVariable" in delay.
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// TODO: Think if it should be public, or private property.
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Variables map[SettableVariable]string
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// Config is a file path to the configuration for Tesseract
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// See http://www.sk-spell.sk.cx/tesseract-ocr-parameters-in-302-version
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// TODO: Fix link to official page
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ConfigFilePath string
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}
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// NewClient construct new Client. It's due to caller to Close this client.
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func NewClient() *Client {
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client := &Client{
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api: C.Create(),
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Variables: map[SettableVariable]string{},
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Trim: true,
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}
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return client
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}
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// Close frees allocated API. This MUST be called for ANY client constructed by "NewClient" function.
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func (client *Client) Close() (err error) {
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// defer func() {
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// if e := recover(); e != nil {
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// err = fmt.Errorf("%v", e)
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// }
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// }()
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C.Clear(client.api)
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C.Free(client.api)
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if client.pixImage != nil {
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C.DestroyPixImage(client.pixImage)
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client.pixImage = nil
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}
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return err
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}
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// SetImage sets path to image file to be processed OCR.
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func (client *Client) SetImage(imagepath string) error {
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if client.api == nil {
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return fmt.Errorf("TessBaseAPI is not constructed, please use `gosseract.NewClient`")
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}
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if imagepath == "" {
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return fmt.Errorf("image path cannot be empty")
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}
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if _, err := os.Stat(imagepath); err != nil {
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return fmt.Errorf("cannot detect the stat of specified file: %v", err)
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}
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if client.pixImage != nil {
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C.DestroyPixImage(client.pixImage)
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client.pixImage = nil
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}
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p := C.CString(imagepath)
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defer C.free(unsafe.Pointer(p))
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img := C.CreatePixImageByFilePath(p)
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client.pixImage = img
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return nil
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}
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// SetImageFromBytes sets the image data to be processed OCR.
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func (client *Client) SetImageFromBytes(data []byte) error {
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if client.api == nil {
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return fmt.Errorf("TessBaseAPI is not constructed, please use `gosseract.NewClient`")
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}
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if len(data) == 0 {
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return fmt.Errorf("image data cannot be empty")
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}
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if client.pixImage != nil {
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C.DestroyPixImage(client.pixImage)
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client.pixImage = nil
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}
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img := C.CreatePixImageFromBytes((*C.uchar)(unsafe.Pointer(&data[0])), C.int(len(data)))
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client.pixImage = img
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return nil
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}
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// SetLanguage sets languages to use. English as default.
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func (client *Client) SetLanguage(langs ...string) error {
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if len(langs) == 0 {
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return fmt.Errorf("languages cannot be empty")
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}
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client.Languages = langs
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return nil
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}
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// SetWhitelist sets whitelist chars.
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// See official documentation for whitelist here https://github.com/tesseract-ocr/tesseract/wiki/ImproveQuality#dictionaries-word-lists-and-patterns
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func (client *Client) SetWhitelist(whitelist string) error {
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return client.SetVariable(TESSEDIT_CHAR_WHITELIST, whitelist)
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}
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// SetBlacklist sets whitelist chars.
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// See official documentation for whitelist here https://github.com/tesseract-ocr/tesseract/wiki/ImproveQuality#dictionaries-word-lists-and-patterns
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func (client *Client) SetBlacklist(whitelist string) error {
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return client.SetVariable(TESSEDIT_CHAR_BLACKLIST, whitelist)
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}
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// SetVariable sets parameters, representing tesseract::TessBaseAPI->SetVariable.
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// See official documentation here https://zdenop.github.io/tesseract-doc/classtesseract_1_1_tess_base_a_p_i.html#a2e09259c558c6d8e0f7e523cbaf5adf5
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// Because `api->SetVariable` must be called after `api->Init`, this method cannot detect unexpected key for variables.
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// Check `client.setVariablesToInitializedAPI` for more information.
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func (client *Client) SetVariable(key SettableVariable, value string) error {
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client.Variables[key] = value
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return nil
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}
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// SetPageSegMode sets "Page Segmentation Mode" (PSM) to detect layout of characters.
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// See official documentation for PSM here https://github.com/tesseract-ocr/tesseract/wiki/ImproveQuality#page-segmentation-method
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// See https://github.com/otiai10/gosseract/issues/52 for more information.
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func (client *Client) SetPageSegMode(mode PageSegMode) error {
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C.SetPageSegMode(client.api, C.int(mode))
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return nil
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}
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// SetConfigFile sets the file path to config file.
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func (client *Client) SetConfigFile(fpath string) error {
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info, err := os.Stat(fpath)
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if err != nil {
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return err
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}
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if info.IsDir() {
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return fmt.Errorf("the specified config file path seems to be a directory")
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}
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client.ConfigFilePath = fpath
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return nil
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}
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// Initialize tesseract::TessBaseAPI
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// TODO: add tessdata prefix
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func (client *Client) init() error {
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var languages *C.char
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if len(client.Languages) != 0 {
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languages = C.CString(strings.Join(client.Languages, "+"))
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}
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defer C.free(unsafe.Pointer(languages))
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var configfile *C.char
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if _, err := os.Stat(client.ConfigFilePath); err == nil {
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configfile = C.CString(client.ConfigFilePath)
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}
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defer C.free(unsafe.Pointer(configfile))
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res := C.Init(client.api, nil, languages, configfile)
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if res != 0 {
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// TODO: capture and vacuum stderr from Cgo
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return fmt.Errorf("failed to initialize TessBaseAPI with code %d", res)
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}
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if err := client.setVariablesToInitializedAPI(); err != nil {
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return err
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}
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if client.pixImage == nil {
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return fmt.Errorf("PixImage is not set, use SetImage or SetImageFromBytes before Text or HOCRText")
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}
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C.SetPixImage(client.api, client.pixImage)
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return nil
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}
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// This method sets all the sspecified variables to TessBaseAPI structure.
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// Because `api->SetVariable` must be called after `api->Init()`,
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// gosseract.Client.SetVariable cannot call `api->SetVariable` directly.
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// See https://zdenop.github.io/tesseract-doc/classtesseract_1_1_tess_base_a_p_i.html#a2e09259c558c6d8e0f7e523cbaf5adf5
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func (client *Client) setVariablesToInitializedAPI() error {
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for key, value := range client.Variables {
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k, v := C.CString(string(key)), C.CString(value)
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defer C.free(unsafe.Pointer(k))
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defer C.free(unsafe.Pointer(v))
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res := C.SetVariable(client.api, k, v)
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if bool(res) == false {
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return fmt.Errorf("failed to set variable with key(%v) and value(%v)", key, value)
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}
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}
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return nil
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}
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// Text finally initialize tesseract::TessBaseAPI, execute OCR and extract text detected as string.
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func (client *Client) Text() (out string, err error) {
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if err = client.init(); err != nil {
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return
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}
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out = C.GoString(C.UTF8Text(client.api))
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if client.Trim {
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out = strings.Trim(out, "\n")
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}
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return out, err
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}
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// HOCRText finally initialize tesseract::TessBaseAPI, execute OCR and returns hOCR text.
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// See https://en.wikipedia.org/wiki/HOCR for more information of hOCR.
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func (client *Client) HOCRText() (out string, err error) {
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if err = client.init(); err != nil {
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return
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}
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out = C.GoString(C.HOCRText(client.api))
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return
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}
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